Technical Field
The present disclosure relates to a charge pump circuit and a boosting circuit.
Related Art
In technology related to a boosting circuit including a charge pump circuit, the following technology is known. For example, Japanese Patent Application Laid-Open (JP-A) No. H04-162560 discloses a boosting circuit that includes a voltage dividing circuit that divides the voltage of an output voltage of a charge pump circuit using resistor elements, an error amplifier that amplifies an error voltage obtained by comparing a voltage divided by the voltage dividing circuit with a reference voltage, and a voltage-controlled oscillator (VCO) that outputs a switching signal of the charge pump circuit as a voltage to control output of the error amplifier.
Further, JP-A No. 2010-279089 discloses a boosting circuit including a first transistor connected to a first node, a first capacitor element that has a first end connected to the first node and that is charged with the voltage of the first node in a case in which the first transistor is activated, and a first control signal generation circuit that outputs a first control signal to a control terminal of the first transistor. In this boosting circuit, in a case in which the first transistor is not activated, the first capacitor element boosts the potential of the first node to a second voltage by a voltage not exceeding ½ a first power source voltage being applied to the other end of the first capacitor element. In the first control signal generation circuit, the potential of the first control signal in a case in which the first transistor is not activated is a second potential. The second potential is a potential such that the difference between the potential of the first control signal when the first transistor is activated and the second potential is within the first power source voltage.
In JP-A No. 2008-113269, a charge pump circuit is described that includes plural charge transmission elements connected together in series between an input terminal and an output terminal, plural capacitor elements each having one terminal connected to a respective connection point of the plural charge transmission elements and another terminal applied with a clock signal, a step-down circuit that steps down a voltage of the output terminal in a case in which application of the clock signal has stopped, and a step-down rectifier element connected between the connection point and the output terminal.
According to the boosting circuit of JP-A No. H04-162560, the voltage dividing circuit that divides the output voltage of the charge pump circuit is configured by plural resistor elements connected together in series. However, the consumed current may increase by the voltage dividing circuit configured by the plural resistor elements.
On the other hand, in a boosting circuit, a withstand voltage of transistors configuring the boosting circuit needs to be considered. In particular, the withstand voltage of gate oxide films is important, and a circuit configuration needs to be employed such that potential differences between gates and sources and between gate and drains do not exceed the withstand voltages. Generally, in a boosting circuit, circuit blocks applied with a high voltage generated by boosting are configured including high withstand voltage transistors, and other circuit blocks are configured by low withstand voltage transistors. However, high withstand voltage transistors have a different structure to low withstand voltage transistors. In particular, the film thickness of gate oxide film for high withstand voltage transistors is thicker than that for low withstand voltage transistors, with a consequent increase in the number of masks and the number of process employed in the manufacturing processes for high withstand voltage transistors compared to those for low withstand voltage transistors. Thus, the manufacturing cost becomes higher in cases in which a boosting circuit includes a high withstand voltage transistor.